Indonesian police shave mohicans off punks who were seized at a concert. Photograph: Hotli Simanjuntak/EPA

Police in Indonesia's most conservative province have stripped away body piercings and shaved off mohicans from 65 youths detained at a punk-rock concert because of their perceived threat to Islamic values.

The teens and young men were also stripped of dog-collar necklaces and chains and then thrown in pools of water for "spiritual" cleansing, the local police chief, Iskandar Hasan, said on Wednesday.

After replacing their "disgusting" clothes, he handed each a toothbrush and barked: "Use it."

It was the latest effort by authorities to promote strict moral values in Aceh, the only province in this secular but predominantly Muslim nation of 240 million people to have imposed Islamic laws.

Here, adultery is punishable by stoning to death, gay people have been thrown in jail or lashed in public with rattan canes, and women must wear headscarves.

Punk rockers have complained for months about harassment, but Saturday's roundup at a concert attended by more than 100 people was by far the most dramatic.

Baton-wielding police broke up the concert, scattering young music lovers, many of whom had travelled from other parts of the sprawling archipelagic nation.

Dozens were loaded into vans and brought to a police detention centre in the hills, 30 miles (60km) from the provincial capital, Banda Aceh, for rehabilitation, training in military-style discipline and religious classes, including Qur'an recitation.

They will be held there for at least 10 days, after which they will be returned to their parents.

One 20-year-old detainee, Fauzan, was mortified.

"Why? Why my hair?" he said, pointing to his clean-shaven head. "We didn't hurt anyone. This is how we've chosen to express ourselves. Why are they treating us like criminals?"

But the police chief, Hasan, insisted he had done nothing wrong.

"We're not torturing anyone," he said. "We're not violating human rights. We're just trying to put them back on the right moral path."

However, Nur Kholis, a national human rights commissioner, deplored the detention, saying police must explain what criminal laws were violated by the youngsters.

"Otherwise, they violated people's right of gathering and expression," Kholis said, and promised to investigate it.

Aceh was given semi-autonomy as part of a peace deal with Indonesia's central government after the province agreed to end a separatist struggle in 2005.